## MODEL QUESTION PAPER

 Test/Date and Time Semester/year Course/Course Code Max Marks Ex: I test/6 th week of sem 10-11 Am IVSEM REFRIGERATION AND AIR CONDITIONING 20 Year: 2016-17 Course code:15ME63F Name of Course coordinator :                                                                                    Units:1,2 Co: 1,2   Note:  Answer all questions Question no Question MARKS CL CO PO 1 Define 1 ton of refrigeration. Show how one ton refrigeration is expressed in kW. OR Or Explain refrigeration by throttling process with temperature -pressure diagram 05 U 1 2 2 List the advantages and disadvantages of vapour refrigeration over air refrigeration system. 05 R 2 2 3 An ammonia refrigerator produces 20 tones of ice at 00C in 24 hours. The temperature range of the system is -150C. The vapour leaving the compressor’s dry-saturated. Assuming actual COP is 75% of theoretical, calculate the power required to run the compressor. Take latent heat of ice as 335 kJ/kg. Use the following properties of ammonia. 10 A 2 1,2 Saturation temp in 0C Enthalpy(kJ/kg) Entropy(kJ/kg-K) hf hg sf sg 25 99.94 1317.95 0.3469 4.4816 -15 -54.50 1303.74 -0.2132 5.0536

MODEL QUESTION PAPER

VI- Semester Diploma Examination

Course Title: REFRIGERATION AND AIR CONDITIONING

Time: 3 Hours]                                                                                                      [Max                                                                                                   Marks:                                                                                                         100

Note: Answer any SIX from Part A and any SEVEN from Part B

PART-A                                                   6x5=30 marks

1.     Define the following terms:

i.     Refrigeration

ii.     Refrigerating effect

2.     List the advantages and disadvantages of undercooling in the VCR system.

3.     Define compressor, condenser.

4.     Define refrigerant. List the types of refrigerant leak detector

5.     Define following psychrometric properties

a.     WBT

b.     DBT

c.     Humidity

d.     Relative humidity

e.     Dew point temp.

6.     Explain the procedure of adding the oil to compressor

7.     Explain hermetically sealed compressors.

8.     Explain the effect of under cooling on the COP of a vapour compression refrigeration cycle with T-S diagram

9.     Build the expression for volumetric efficiency of reciprocating compressor with P-V diagram.

PART-B                                     7x10=70 marks

1)         a. Explain refrigeration by throttling process with temperature -pressure diagram.                                       05

b. Ice is formed at 00C from water at 200C. The temperature of brine solution is-100C reversible carnot cycle. Latent heat of ice is = 336kj/kg. find the Kg of ice formed per 1kWhr.Assume the refrigeration cycle is

perfect.                                                                             05

2)      Develop an expression for work done and COP of a vapour compression refrigeration cycle(dry saturated) with T-S diagram.

3)      1An ammonia refrigerator produces 20 tones of ice at 00C in 24 hours. The temperature  range of the system is -150C. The vapour leaving the compressor’s dry-saturated. Assuming actual COP is 75% of theoretical, calculate the power required to run the compressor. Take latent heat of  ice as 335 kJ/kg. Use the following properties of ammonia.

 Saturation temp Enthalpy(kJ/kg) Entropy(kJ/kg-K)

 in 0C hf hg sf sg 25 99.94 1317.95 0.3469 4.4816 -15 -54.50 1303.74 -0.2132 5.0536

10

4)      Explain with sketch the natural convection evaporator(with and without                                                                            baffle).

5)      A. Write a note on automatic expansion valve with neat sketch.                                                                 05

B. Explain with sketch the operation of solenoid valve for variable refrigerant flow control.

05

6)   a. Explain  on transport refrigeration. 05

b. List  any five essential properties of good refrigerants.                                                                                   05

7)     a. List  any four different types of air filters used in air conditioning 04

b. Explain bag type dry air filter with sketch.                                                                                  06

8)       Explain the causes for faults in refrigeration system 10

9)      Select the procedure should be adopted for replacing the evaporator(with and without valves) from the system 10

10)   a. Explain with sketch the winter air conditioning system for mild and cold

weather.                                                                                    07

b. Classify refrigerants.                                                                                     03

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### MODEL QUESTION BANK

Diploma in Mechanical Engineering VI Semester

1)      Define the following terms:

i.    Refrigeration

ii.     Refrigerating effect

iii.     Ton of refrigerator

iv.     Heat pump

v.     Refrigerator

vi.     COP

2)      Define 1 ton of refrigeration. Show how one ton refrigeration is expressed in kW.

3)      Name five means of producing refrigeration.

4)      List the advantages and disadvantages liquid nitrogen refrigeration with Specific field of application.

5)     List the advantages and disadvantages Air refrigeration with specific field of application.

UNDERSTANDING

1)    Explain how a refrigerant produces cooling effect?

2)     Explain how the ice can be used for refrigeration? Is it possible to produce the temperature below zero degree with the help of ice?

3)      Compare the direct and indirect refrigeration system with advantages and disadvantages.

4) Explain refrigeration by throttling process with temperature -pressure diagram.

APPLICATION

###### 5)  Make use of sketch explain dry ice refrigeration

6)  Make use of sketch explain Steam jet refrigeration

7)  Make use of sketch Explain liquid nitrogen refrigeration

8)  Make use of sketch Explain Carnot refrigeration Cycle with with PV and TS diagram.

9)  Make use of sketch Explain Air refrigeration/ Bell-Coleman refrigeration Cycle with with PV and TS diagram.

10) Ice is formed at 00C from water at 200C. The temperature of brine solution is-100C reversible carnot cycle. Latent heat of ice is = 336kj/kg.

find the Kg of ice formed per 1kWhr.Assume the refrigeration cycle is perfect

11)                  A Carnot refrigerator extracts 400 kJ of heat per minute from a cold room

which is     maintained at -150 C and it is discharged to atmosphere which is at 300 C. Find an ideal kW-capacity of motor required to run the unit.

12)  A reversed Carnot cycle is used to deliver 1680kJ/sec to heat the conditional space. The heat is taken from atmosphere at 100C and supplied to the conditional space at 250C. Find the followings: If the same quantity of heat is supplied by electric heaters, find the

a.     kW required to run the system

b.    consumption of electric energy in kW.

REMEMBERING

1)      List the advantages and disadvantages of vapour refrigeration over air refrigeration system.

2)     List the advantages and disadvantages of superheating in the VCR system.

3)     List the advantages and disadvantages of under cooling in the VCR system.

UNDERSTANDING

###### 1)    Compare vapour compression refrigeration system over vapour absorption refrigeration system.

APPLICATION

###### 2)    Make use of a flow diagram Explain the working principle of vapour compression refrigeration cycle.

3)    Make use of P-v and T-S diagram explain the working of vapour compression refrigeration cycle.

4)    Develop an expression for work done and COP of a vapour compression refrigeration cycle (dry saturated) with T-S diagram.

5)    Develop an expression for work done and COP of a vapour compression refrigeration cycle (superheated) with T-S diagram.

6)    Make use of T-S diagram explain the effect of under cooling on the COP of a vapour compression refrigeration cycle

7)    Make use of T-S diagram Explain the effect of superheating on the COP of a vapour compression refrigeration cycle .

8)    Make use of a flow diagram Explain the working principle of simple vapour absorption refrigeration cycle.

9)    Make use of a flow diagram Explain the working principle of ammonia absorption refrigeration cycle.

10)  Make use of a flow diagram Explain the working principle of Domestic Electrolux refrigeration cycle.

11)  An ammonia refrigerator produces 20 tones of ice at 00C in 24 hours. The temperature range of the system is -150C. The vapour leaving the compressor’s dry- saturated. Assuming actual COP is 75% of theoretical, calculate the power required to run the compressor. Take latent heat of ice as 335 kJ/kg. Use the following properties of ammonia.

 Saturation temp in 0C Enthalpy(kJ/kg) Entropy(kJ/kg-K) hf hg sf sg 25 99.94 1317.95 0.3469 4.4816 -15 -54.50 1303.74 -0.2132 5.0536

12)    An ammonia refrigerator works between -6.70C and 260C. The vapour is dry saturated at the end of compression. Calculate

a.     Theoretical COP

b.    Power required to drive the compressor.

If the cooling capacity of the refrigerant is 5 tons. Use the following properties of ammonia(NH3)

 Saturation temp in 0C Specific Enthalpy(kJ/kg) Specific Entropy(kJ/kg-K) Liquid hf Saturated vapour hg Liquid sf Saturated vapour sg -6.7 -29.26 1262.36 0.1087 4.7401 26.7 124.56 1291.62 0.4264 4.3263

REMEMBER

###### 1)    Define compressor.

2)    List the different types of compressors.

3)    Define volumetric efficiency of a compressor.

4)    Define condenser.

5)    List the different types of condensers.

6)    Define evaporator.

7)    List the different types of evaporators.

8)    List the different types of expansion devices.

UNDERSTANDING

1)    Explain hermetically sealed compressors.

2)    Explain with reasons the fields of applications of each type of                               compressor in the refrigeration system.

3)    Outline the advantages and disadvantages of centrifugal compressor over the reciprocating compressor.

4)    Compare air-cooled and water-cooled condensers.

5)    Explain the functions of expansion devices.

APPLICATION

###### 1)            Make use of P-V diagram Explain the cycle of working of reciprocating compressor

2)            Make use of flow and P-H diagram Explain the working of centrifugal compressor

3)             Make use of sketch Explain the working of air cooled condenser

4)             Make use of sketch Explain the working of water cooled condenser

5)            Make use of sketch Explain the natural convection evaporator(with and without baffle).

6)             Make use of sketch Explain the forced convection evaporator.

7)             Make use of sketch explain automatic expansion valve with neat sketch.

8)            Make use of sketch Explain the operation of solenoid valve for high temperature in evaporators.

9)             Make use of sketch Explain the operation of solenoid valve for low temperature in evaporators.

10)         Make use of sketch Explain the operation of solenoid valve for variable refrigerant flow control.

CO4: Know the different types of refrigerants and Application of refrigeration to various areas

REMEMBER

### 1)    Define refrigerant.

2)    List the types of leak detector.

UNDERSTANDING

1)    Classify refrigerants.

2)    Explain the factors affecting the choice of refrigerants commonly used in refrigerating plants.

3)    Outline the essential properties of good refrigerants.

4)    Outline the factors are considered in selecting refrigerants in the following system and name the refrigerant in each system

a.     House hold refrigerator.

b.    Ice producing plant.

c.     Air conditioning plant.

5)    Explain electronic leak detector.

APPLICATION

1)    Choose the various factors to be considered to design cold storage

2)    Choose the various factors to be considered to design quick freezing.

CO5: Appreciate the concept of Air Conditioning and know their types

REMEMBERING

1.    Define Air conditioning.

2.    List different factors affecting air conditioning.

3.    Define psychrometry.

4.    List and define psychrometric properties.

5.    List different air conditioning equipments.

6.    List different types of air filters used in air conditioning.

7.    List different types of humidifiers used in air conditioning.

8.    List different types of dehumidifiers used in air conditioning.

9.    List different types of blowers used in air conditioning. 10.List the major difference between fans and blowers.

1. Explain briefly different factors affecting air conditioning.

1.    Make use of sketch Explain psychrometric chart

2.    Make use of sketch Explain sensible heating

3.    Make use of sketch Explain sensible Cooling

4.    Make use of sketch Explain the summer air conditioning system for hot and dry outdoor conditions.

5.    Make use of sketch Explain the summer air conditioning system for hot and humid outdoor conditions.

6.    Make use of sketch Explain the winter air conditioning system for mild and cold weather.

7.    Make use of sketch explain the following

a.     Cooling with dehumidification

b.    Cooling with adiabatic humidification of air

c.      Cooling with dehumidification.

8.    Make use of sketch Explain Steam injection type humidifier.

9.    Make use of sketch Explain Spray type dehumidifier. 10.Make use of sketch Explain Axial flow fans. 11.Make use of sketch Explain centrifugal flow fans.

CO6: Familiarize the different tools used to install refrigeration system and Air Conditioner

UNDERSTANDING

1)      Explain the different instruments used for the measurement of temperature, pressure, electricity, velocity of air and flow of air(Ref. Basic Refrigeration and Air Conditioning-P N Ananthanarayanan)

2)     Explain the installation procedure for refrigerating units.

3)     Explain the charging of refrigerating unit with neat sketch.

4)     Explain the procedure of adding the oil to compressor.

5)     Explain the different tests for refrigerants leakage.

6)     Explain the procedure of removing the compressor from refrigeration non sealed unit.

7)     Explain the procedure of removing the compressor from refrigeration sealed unit.

8)     Explain the steps to be followed before disconnecting the condenser from the refrigeration system.

9)     Explain the procedure should be adopted for replacing the evaporator(with and without valves) from the system.

10) Outline the points should be remembered for the maintenance of household refrigerator

11)             Explain the causes for faults in refrigeration system.